The present invention relates to an isolation mount used in securing a vehicle body to a support structure, such as a vehicle cradle mount or subframe, and for absorbing vibrations and movements between the two structures.
Subframe mounts are used extensively in unibody vehicles to isolate the vibration which is transmitted from the engine to the subframe and the body. The subframe mount also improves vehicle dynamics by providing vertical stiffness, lateral stiffness and fore and aft stiffness and their respective stiffness rates. The operator of the vehicle perceives that vibration isolation relates to ride quality and that improved vehicle dynamics translates into improved handling performance.
Typically, there are as many as four locations on the subframe where an isolation mount is utilized. The subframe is sandwiched between the upper portion and the lower portion of the vibration mount and the vehicle body rests on top of the upper mount. A bolt extends through an aperture in the frame and the isolation mount. The lower mount and then the upper mount are connected by a cage nut on the body to complete the attachment, of the body to the subframe. The mount isolates engine or transmission induced vibration that is transmitted along the subframe to the body. The mount also improves vehicle dynamics by controlling or attenuating relative movement between the vehicle body and subframe in the vertical mode or plane, that is up and down, relative movement, and also to control lateral mode or plane, that is side to side movement, and fore and aft mode or plane, that is front to back relative movement.,
A typical design of a subframe isolation mount employs a relatively hard or high durometer rubber (typically 40 to 80 Shore A) as an isolating material. High durometer rubber for cradle or subframe mounts is an excellent material for improved handling in the lateral plane, especially when it is combined with rate plates to stiffen the response in the lateral plane and to a limited degree the fore and aft plane. However, since the solid elastomeric material is generally very stiff, it does not control or attenuate vertical forces from the subframe to the body very effectively. As a result, the isolation mount has a high lateral stiffness rate response which is desirable but it has a fore and aft stiffness rate response which is marginally acceptable and a vertical stiffness rate response which is low. Therefore, good ride and handling of a vehicle are compromised because of the stiffness properties of the solid elastomeric material.
Thus, there is a need for a vibration isolation mount that provides for ride quality that is satisfactory to the operator without sacrificing the handling characteristics of the vehicle in the lateral plane, fore and aft plane and vertical plane. Additionally, there is a need for a mount that is lighter in weight, improves durability and reduces both initial and high mileage noise, vibration, and harshness between a subframe and a body.
The present invention discloses an isolation mount for motor vehicles having a subframe or cradle and a body. The body has an aperture and the subframe has a through hole. The isolation mount includes a foamed elastomeric annular upper isolation member between the body and the subframe. The foamed elastomeric insert member is disposed in the annular upper member and extends therefrom. The insert member has an elliptical inner axial passageway. An elliptical isolation member extends from the upper isolation member and is contiguous to the elliptical inner axial passageway of the insert member. The elliptical isolation member has a cross sectional area and a passageway. The cross sectional area has a major axis and a minor axis. The major axis provides control or attenuation for lateral vibration and the minor axis provides control or attenuation for fore and aft vibration. An elliptical retainer member is disposed in the passageway. The retainer has a bore. The annular lower isolation member is mounted to the opposite subframe opposite the annular upper isolation member. The annular lower isolation member and the annular upper isolation member provide control or attenuation for vertical vibration. Thus, a simpler, more cost effective isolation mount is provided which improves vehicle dynamics between the body and the subframe in the vertical direction, lateral direction and fore and aft directions.
It is an object of the present invention to provide a foamed elastomeric isolation mount with an elliptical insert which attenuates the vibration transmitted from the subframe to the body as well as providing improved vertical mode, lateral mode, and fore and aft mode stiffness for improved vehicle dynamics.
It is another object of the present invention to provide an isolation mount with an elliptical insert which utilizes foamed elastomeric upper and lower mounts which isolate vibration transmitted from the subframe to the body, as well as providing low vertical stiffness, high lateral stiffness and moderate fore and aft stiffness to improve handling performance of the vehicle.
These and other features of the present invention will become apparent from the subsequent descriptions and drawings.